Try right clicking on each folder and verifying the Properties. Write down the path (the actual location of the folder) for the duplicate folder, and make sure it isn't marked as read only. If the folder exists in your personal profile (i.e. C:|Documents and Settings\username) Log off from your account, and log back in with the local Administrator account. Open Windows Explorer, find the second folder and delete it.
This was first published in March 2004